In recent years, there has been proposed an ultrasonic motor which moves a small-sized movable element of a lens or the like in high-accuracy by using a minute vibration of a piezoelectric element as a driving source.
Relating to these kinds of ultrasonic motors, in Japanese unexamined patent publication H7-184382, there is described a technology in which a rectangular piezoelectric element is divided equally into four portion-areas by orthogonal two line segments parallel to the sides thereof and electrodes are respectively provided thereon and concurrently, an asymmetric unipolar pulse voltage is electrically-conducted by changing-over those electrodes. As compared in FIG. 3 and FIG. 5 of H7-184382, this ultrasonic motor reverses the resonance direction of the piezoelectric element for the right and left directions by changing-over the selection of the diagonal two electrodes to be conducted with the pulse voltage. Then, as shown in FIG. 7 of H7-184382, this ultrasonic motor bending-vibrates such that the long side of the rectangular piezoelectric element will be bent.